Cerebral perfusion augmentation

ABSTRACT

Methods are provided for partial aortic occlusion for cerebral perfusion augmentation in patients suffering from global or focal cerebral ischemia. A catheter is advanced into the descending aorta, the catheter having a proximal region, a distal region, and an expandable member mounted on the distal region. The expandable member is located downstream from the takeoff of a carotid artery. The expandable member is expanded to at least partially obstruct blood flow in the aorta. A physiologic parameter is measured that indicates adequacy of cerebral perfusion. The expansion of the expandable member is adjusted based on the measured physiologic parameter. Other medical devices, such as an atherectomy catheter, can be inserted distal the occluder to provide therapeutic intervention.

[0001] This is a continuation of U.S. application Ser. No. 09/531,443,filed Mar. 20, 2000, which is a divisional of U.S. application Ser. No.09/260,371, filed Mar. 1, 1999, now U.S. Pat. No. 6,231,551. All of theabove patents and applications are incorporated herein by reference intheir entirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to medical devices. Moreparticularly, the invention relates to methods and devices foraugmenting blood flow to a patient's vasculature. More particularly, theinvention relates to apparatus and methods which provide partialobstruction (“coarctation”) to aortic blood flow to augment cerebralperfusion in patients with global or focal ischemia. The devices andmethods also provide mechanisms for continuous constriction and variableblood flow through the aorta.

BACKGROUND OF THE INVENTION

[0003] Patients experiencing cerebral ischemia often suffer fromdisabilities ranging from transient neurological deficit to irreversibledamage (stroke) or death. Cerebral ischemia, i.e., reduction orcessation of blood flow to the central nervous system, can becharacterized as either global or focal. Global cerebral ischemia refersto reduction of blood flow within the cerebral vasculature resultingfrom systemic circulatory failure caused by, e.g., shock, cardiacfailure, or cardiac arrest. Shock is the state in which failure of thecirculatory system to maintain adequate cellular perfusion results inreduction of oxygen and nutrients to tissues. Within minutes ofcirculatory failure, tissues become ischemic, particularly in the heartand brain.

[0004] The most common form of shock is cardiogenic shock, which resultsfrom severe depression of cardiac performance. The most frequent causeof cardiogenic shock is myocardial infarction with loss of substantialmuscle mass. Pump failure can also result from acute myocarditis or fromdepression of myocardial contractility following cardiac arrest orprolonged cardiopulmonary bypass. Mechanical abnormalities, such assevere valvular stenosis, massive aortic or mitral regurgitation,acutely acquired ventricular septal defects, can also cause cardiogenicshock by reducing cardiac output. Additional causes of cardiogenic shockinclude cardiac arrhythmia, such as ventricular fibrillation.

[0005] Treatment of global cerebral ischemia involves treating thesource of the systemic circulatory failure and ensuring adequateperfusion to the central nervous system. For example, treatment ofcardiogenic shock due to prolonged cardiopulmonary bypass consists ofcardiovascular support with the combination of inotropic agents such asdopamine, dobutamine, or amrinone and intra-aortic ballooncounterpulsation. Vasoconstrictors, such as norepinephrine, are alsoadministered systemically to maintain systolic blood pressure (atapproximately above 80 mmHg). Unfortunately, these agents produce apressure at the expense of flow, particularly blood flow to smallvessels such as the renal arteries. The use of the vasoconstrictors is,therefore, associated with significant side effects, such as acute renalfailure.

[0006] Focal cerebral ischemia refers to cessation or reduction of bloodflow within the cerebral vasculature resulting from a partial orcomplete occlusion in the intracranial or extracranial cerebralarteries. Such occlusion typically results in stroke, a syndromecharacterized by the acute onset of a neurological deficit that persistsfor at least 24 hours, reflecting focal involvement of the centralnervous system and is the result of a disturbance of the cerebralcirculation. Other causes of focal cerebral ischemia include vasospasmdue to subarachnoid hemorrhage or iatrogenic intervention.

[0007] Traditionally, emergent management of acute ischemic strokeconsists of mainly general supportive care, e.g. hydration, monitoringneurological status, blood pressure control, and/or anti-platelet oranti-coagulation therapy. Heparin has been administered to strokepatients with limited and inconsistent effectiveness. In somecircumstances, the ischemia resolves itself over a period of time due tothe fact that some thrombi get absorbed into the circulation, orfragment and travel distally over a period of a few days. In June 1996,the Food and Drug Administration approved the use of tissue plasminogenactivator (t-PA) or Activase®, for treating acute stroke. However,treatment with systemic t-PA is associated with increased risk ofintracerebral hemorrhage and other hemorrhagic complications. Aside fromthe administration of thrombolytic agents and heparin, there are notherapeutic options currently on the market for patients suffering fromocclusion focal cerebral ischemia. Vasospasm may be partially responsiveto vasodilating agents. The newly developing field of neurovascularsurgery, which involves placing minimally invasive devices within thecarotid arteries to physically remove the offending lesion may provide atherapeutic option for these patients in the future, although this kindof manipulation may lead to vasospasm itself.

[0008] In both global and focal ischemia, patients develop neurologicdeficits due to the reduction in cerebral blood flow. Treatments shouldinclude measures to increase blood flow to the cerebral vasculature tomaintain viability of neural tissue, thereby increasing the length oftime available for interventional treatment and minimizing neurologicdeficit while waiting for resolution of the ischemia. Augmenting bloodflow to the cerebral vasculature is not only useful in treating cerebralischemia, but may also be useful during interventional procedures, suchas carotid angioplasty, stenting or endarterectomy, which mightotherwise result in focal cerebral ischemia, and also cardiac procedureswhich may result in global cerebral ischemia, such as cardiaccatheterization, electrophysiologic studies, and angioplasty.

[0009] New devices and methods are thus needed for augmentation ofcerebral blood flow in treating patients with either global or focalischemia caused by reduced perfusion, thereby minimizing neurologicdeficits.

SUMMARY OF THE INVENTION

[0010] The invention provides vascular constriction devices and methodsfor augmenting blood flow to a patient's cerebral vasculature, includingthe carotid and vertebral arteries. The devices constructed according tothe present invention comprise a constricting mechanism distally mountedon a catheter for delivery to a vessel, such as the aorta. Theconstrictor is collapsed to facilitate insertion into and removal fromthe vessel, and expanded during use to restrict blood flow. Whenexpanded, the constrictor has a maximum periphery that conforms to theinner wall of the vessel, thereby providing a sealed contact between itand the vessel wall. The constrictor typically has a blood conduitallowing blood flow from a location upstream to a location downstream.The devices further include a variable flow mechanism in operativeassociation with the blood conduit, thereby allowing blood flow throughthe conduit to be adjusted and controlled. The devices can optionallyinclude a manometer and/or pressure limiter to provide feedback to thevariable flow mechanism for precise control of the upstream anddownstream blood pressure. Other medical devices, such as an infusion,atherectomy, angioplasty, hypothermia catheters or devices (selectivecerebral hypothermia with or without systemic hypothermia, and typicallyhypothermia will be combined with measures to increase perfusion toovercome the decreased cerebral blood flow caused by the hypothermia,such that hypothermia and coarctation are complimentary), orelectrophysiologic study (EPS) catheter, can be introduced through theconstrictor to insert in the vessel to provide therapeutic interventionsat any site rostrally.

[0011] In a preferred embodiment, the expandable constrictor comprisesan outer conical shell and an inner conical shell. Each shell has anapex and an open base to receive blood flow. One or a plurality of portstraverses the walls of the two conical shells. Blood flows through theopen base and through the ports. The inner shell can be rotated relativeto the outer shell so that the ports align or misalign with the ports inthe outer shell to allow variable blood flow past the occluder, therebyproviding adjustable and controlled flow. The inner shell is rotated bya rotating mechanism, e.g., a torque cable disposed within the elongatetube and coupled to the inner shell. The constrictor can be expanded by,e.g., a resilient pre-shaped ring, graduated rings, or a beveled lipformed at the base of the shell, and collapsed by, e.g., pull wiresdistally affixed to the occluder or a guide sheath.

[0012] In another embodiment, the outer conical shell includes aplurality of resilient flaps, which are pivotally affixed to the base orthe apex and can be displaced to variably control blood flow through theconduit. The flaps can be displaced by a plurality of pull wires affixedto the flaps.

[0013] In still another embodiment, the constrictor comprises a firstcylindrical balloon mounted to a distal end of the catheter, and asecond toroidal balloon disposed about the cylindrical balloon. Thechamber of the first balloon communicates with an inflation lumen. Bloodflow occurs through the cylindrical balloon and through the center ofthe toroidal balloon. The toroidal balloon is expanded by inflationthrough a second and independent inflation lumen to reduce blood flowthrough the cylindrical balloon. In this manner, the first balloonprovides an inflatable sleeve and the second toroidal balloon providesvariable control of blood flow through the sleeve. Other embodimentsinclude an expandable sleeve (not a balloon) surrounded by a toroidalballoon for adjustably constricting the flow of blood through thecylindrical sleeve.

[0014] In a preferred method, the occlusion devices described above areinserted into the descending aorta through an incision on a peripheralartery, such as the femoral, subclavian, axillary or radial artery, in apatient suffering from global or focal cerebral ischemia, during cardiacsurgery (including any operation on the heart, with or without CPB), orduring aortic surgery (during circulatory arrest, as for aortic archsurgery, repair of an abdominal aortic aneurysm, or thoracie aneurysmrepair, to reduce perfusion and the amount of blood loss in theoperating field). The devices can be introduced over a guide wire. Withassistance of transesophageal echocardiography (TEE), transthoracicechocardiography (TTE), intravascular ultrasound (IVUS), aortic archcutaneous ultrasound, or angiogram, the constrictor is positioneddownstream from the takeoff of the brachiocephalic artery and upstreamfrom the renal arteries. The constrictor is expanded to partiallyocclude blood flow in the aorta and maintained during systole, duringdiastole, or during systole and diastole. The constrictor preferablyachieves continuous apposition to the wall of the vessel, resulting infewer emboli dislodgment. The pressure limiter, connected to the rotaryunit and the pressure monitor, prevents the upstream and downstreamblood pressure from exceeding, respectively, a set maximum and minimumpressure differential.

[0015] Flow rates can be varied within one cardiac cycle (e.g., 80%during systole, 20% during diastole, or 70% during systole, 30% duringdiastole), and every few cycles or seconds (e.g., 80% for 6 cycles, 20%for 2 cycles, or 70% for 5 cycles, 10% for 1 cycle). In certain cases itmay be preferred to cycle to cycle between lesser and greater occlusionso that the brain does not autoregulate. This ensures constant andcontinued increased cerebral perfusion. In this manner, blood in thedescending aorta is diverted to the cerebral vasculature, therebyincreasing cerebral perfusion and minimizing neurological deficits. Byselectively increasing cerebral blood flow, the use of systemicallyadministered vasoconstrictors or inotropic agents to treat shock may bereduced or eliminated.

[0016] In another method, in patients anticipating a majorcardiothoracic surgery, such as abdominal aortic aneurysm repair, thedevice is introduced and deployed approximately 24 hours prior tosurgery, thereby inducing mild artificial spinal ischemia. This inducesendogenous neuroprotective agents to be released by the spinal cordand/or brain in response to the ischemia, thereby protecting the tissuefrom ischemic insult of surgery. This technique is known as“conditioning”. The devices are inserted into the descending aorta. Toinduce spinal ischemia, the constrictor is positioned downstream fromthe takeoff of the brachiocephalic artery and upstream from the renalartery and expanded to partially occlude blood flow in the aorta,resulting in reduction of blood flow to the spinal cord. A similartechnique may be employed to condition the brain to stimulate productionof neuroprotective agents. To induce cerebral ischemia, the constrictoris positioned upstream from the takeoff of the innominate artery, orbetween the innominate artery and the left common carotid artery.

[0017] Prolonged hypertension often causes ischemic damage to thekidneys. In still another method, the partial occlusion devices areintroduced peripherally and positioned in the renal arteries to reduceblood pressure to the renal vasculature, thereby minimizing damage tothe kidneys that might otherwise result from hypertension.

[0018] It will be understood that there are many advantages in using thepartial aortic occlusion devices and methods disclosed herein. Forexample, the devices can be used (1) to provide variable partialocclusion of a vessel; (2) to augment and maintain cerebral perfusion inpatients suffering from global or focal ischemia; (3) to condition thebrain or spinal cord to secrete neuroprotective agents prior to a majorsurgery which will necessitate reduced cerebral or spinal perfusion; (4)to prolong the therapeutic window in global or focal ischemia; (5) toaccommodate other medical devices, such as an atherectomy catheter; (6)prophylactically by an interventional radiologist, neuroradiologist, orcardiologist in an angiogram or fluoroscopy suite; (7) for prevention ofcerebral ischemia in patients undergoing procedures, such as coronarycatheterization or surgery, where cardiac output might fall as a resultof arrhythmia, myocardial infarction or failure; (8) to treat shock,thereby eliminating or reducing the use of systemic vasoconstrictors;and (8) to prevent renal damage in hypertensives.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 illustrates a patient's systemic arterial circulationrelevant to the present invention.

[0020]FIG. 2 illustrates an embodiment of the devices constructedaccording to the present invention for providing partial occlusion of avessel.

[0021]FIG. 3 illustrates a constrictor of the device depicted in FIG. 2.

[0022]FIG. 4A illustrates an outer conical shell employed in theconstrictor of FIG. 3.

[0023]FIG. 4B illustrates an inner conical shell employed in theconstrictor of FIG. 3.

[0024]FIG. 5 illustrates an alternative embodiment of the constrictorsof FIG. 3 having elongate rectangular ports.

[0025]FIG. 6 illustrates another embodiment of the occluder having abeveled lip.

[0026]FIG. 7 illustrates another embodiment of the occluder having aplurality of graduated rings.

[0027]FIG. 8 illustrates complete misalignment of the ports on the outerand inner conical shells.

[0028]FIG. 9 illustrates partial alignment of the ports on the outer andinner conical shells.

[0029]FIG. 10 illustrates complete alignment of the ports on the outerand inner conical shells.

[0030]FIG. 11 illustrates another embodiment of the device for providingpartial occlusion of a vessel.

[0031]FIG. 12 illustrates another embodiment of the constrictor employedin the device of FIG. 11.

[0032]FIG. 13A illustrates a frontal view of the constrictor of FIG. 12having a plurality of preformed flaps extending perpendicular to thelongitudinal axis of the constrictor.

[0033]FIG. 13B illustrates a frontal view of the flaps of FIG. 13A underan external force.

[0034]FIG. 13C illustrates a frontal view of the constrictor of FIG. 12having a plurality of preformed flaps extending parallel to thelongitudinal axis of the constrictor.

[0035]FIG. 13D illustrates a frontal view of the flaps of FIG. 13C underan external force.

[0036]FIG. 14 illustrates another embodiment of the occluder havingflaps included in the collar of the outer conical shell.

[0037]FIG. 15 illustrates still another embodiment of the device forproviding partial occlusion of a vessel.

[0038]FIG. 16 illustrates an embodiment of the constrictor employed inthe device of FIG. 15.

[0039]FIG. 17 illustrates the constrictor of FIG. 16, having an inflatedring-shaped balloon for reducing blood flow through a blood conduit.

[0040]FIG. 18 illustrates the occluder of FIG. 16, having a deflatedring-shaped balloon.

[0041]FIG. 19 illustrates a suction/atherectomy catheter introducedthrough the constrictor of FIG. 16.

[0042]FIG. 20 illustrates a perfusion and an EPS catheter introducedthrough the constrictor of FIG. 16.

[0043]FIG. 21A illustrates the constrictor of FIG. 3 inserted in theaorta downstream from the left subclavian artery and partially occludingaortic blood flow.

[0044]FIG. 21B illustrates the constrictor of FIG. 14 inserted in theaorta downstream from the left subclavian artery and partially occludingaortic blood flow.

[0045]FIG. 22 illustrates the constrictor of FIG. 3 inserted in theaorta downstream from the right brachiocephalic artery and partiallyoccluding aortic blood flow.

[0046]FIG. 23 illustrates a suction/atherectomy catheter introducedthrough the constrictor of FIG. 3 and inserted in the left carotidartery proximal to a thromboembolic occlusion.

[0047]FIG. 24 illustrates the constrictor of FIG. 3 inserted in theaorta upstream from the lumbar or lumbar or spinal arteries.

[0048]FIG. 25 illustrates the constrictor of FIG. 3 inserted in therenal arteries.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] The devices and methods disclosed herein are most useful intreating patients suffering from global cerebral ischemia due tosystemic circulatory failure, and focal cerebral ischemia due tothromboembolic occlusion of the cerebral vasculature. However, it willbe understood that the devices and methods can be used in other medicalconditions, such as hypertension and spinal cord conditioning.

[0050] Systemic arterial circulation relevant to the methods of thepresent invention is described in FIG. 1. During systole, oxygenatedblood leaving heart 8 enters aorta 10, which includes ascending aorta12, aortic arch 14, and descending aorta 22. The aortic arch gives riseto brachiocephalic trunk 16, left common carotid artery 18, and leftsubclavian artery 20. The brachiocephalic trunk branches into rightcommon carotid artery 24 and right subclavian artery 26. The right andleft subclavian arteries, respectively, give rise to right vertebralartery 28 and left vertebral artery 34. The descending aorta gives riseto a multitude of arteries, including lumbar (i.e., spinal) arteries 38,which perfuse the spinal cord, renal arteries 40, which perfuse thekidneys, and femoral arteries 42, which perfuse the lower extremities.

[0051]FIG. 2 depicts occlusion catheter 100 for use in the methodsdescribed herein. The device includes elongate catheter 102, distallymounted expandable constrictor, i.e., occluder, 104 having distalopening 124 and variable flow mechanism 108. The constrictor, whenexpanded, has maximum periphery 110, which conforms to the inner wall ofa vessel to form a secure seal with the vascular wall, such that bloodflow through the vessel can be effectively controlled. Opening 124receives blood from distal the constrictor and controls the passage ofblood proximal the constrictor. Variable flow mechanism 108, connectedto rotary unit 150, operates the constrictor, thereby controlling (1)the flow rate through the occlusion, and (2) upstream blood pressure.Preferably, the device includes manometer 112, which is connected topressure monitor 156 and pressure limiter 114. Rotary unit 150 receivesblood pressure measurements from the manometer. Pressure limiter 114,connected to the rotary unit and the pressure monitor, prevents theupstream and downstream blood pressure from exceeding, respectively, aset maximum and minimum pressure differential. A proximal end of thecatheter is equipped with adapter 103, from which pull wires 132 can bemanipulated for collapsing the occluder and to which the rotary unit,pressure monitor, and/or pressure limiter can be connected.

[0052] Referring to FIG. 3, the occlusion device comprises catheter 102and constrictor 104. The catheter is constructed from a biocompatibleand flexible material, e.g., polyurethane, polyvinyl chloride,polyethylene, nylon, etc. The catheter includes lumen 116 through whichvarious operative elements pass. Alternatively, the catheter may includemore than one lumen to support various operative elements. The catheteralso includes proximal adapter 103 (see FIG. 2), which provides aninterface between the catheter and the various instruments received bythe catheter. The occluding mechanism consists of outer conical shell118 and inner conical shell 136, each having a distal open base and aproximal apex. Pre-shaped ring 130 is affixed to base 120 of the outershell to facilitate expansion of the constrictor. The ring is formed ofa resilient material, capable of expanding the occluder to achieve amaximum periphery, which is defined by the outer circumference of thering. Ring 130, may, in certain embodiments, further include ananchoring mechanism, such as hooks, bonded to the outer circumference ofthe ring. Expansion of the ring causes the grasping structure to engagethe surface of the vessel wall, thereby securing the occluder andpreventing displacement in the vessel due to force exerted by bloodflow. In other embodiments, the anchoring is provided by an adhesivestrip, vacuum, or merely by frictional engagement of the vessel lumen bythe ring.

[0053] The constrictor can be collapsed to facilitate insertion into andremoval from a vessel. A plurality of pull wires 132 (FIG. 2) aredisposed within torque cable 148, and are distally connected to base 120of outer shell 118 and proximally passes through adapter 103. Theconstrictor is collapsed by applying a tensile force on wires 132, usingtorque cable 148 to provide leverage to the pull wires, thereby drawingthe circumference of the open base 120 towards its center and collapsingthe occluder. A guide sheath (not shown) can be alternatively used tocollapse the constrictor. Using this technique, the guide sheath wouldcover the constrictor and be withdrawn to release the constrictor andadvanced to collapse the constrictor.

[0054] Opening 124 is formed in base 138 and 120 of the respective innerand outer conical shells to provide an inlet for blood flow. Conicalinterior 106 communicates with ports 128 of the outer shell. When theconstrictor is deployed, blood flows into opening 124, through interior106, and exits through ports 128. The occluding mechanism comprisesinner conical shell 136 (partially shown in phantom in FIG. 3), which isrotatably disposed within outer shell 118 as shown in FIGS. 8, 9, and10. The inner shell can be rotated relative to the outer shell throughtorque cable 148, which is disposed in lumen 116 of catheter 102.

[0055] Manometer 112 comprises upstream pressure tube 152 and downstreampressure tube 154, both connected proximally to a pressure monitor toprovide respective blood pressure measurements upstream and downstreamthe constrictor. The upstream pressure tube extends distal to opening124, or may be attached to the inner shell. The downstream pressure tubeextends through an orifice in the catheter proximal to the constrictor.The upstream and downstream blood pressure measurements are recorded anddisplayed by the pressure monitor at a proximal end of the catheter. Apressure limiter, programmed with a maximum pressure threshold to limitthe upstream blood pressure and a minimum pressure threshold to limitthe downstream blood pressure, is connected to the pressure monitor toreceive pressure measurements therefrom, and transmits information to arotary unit. The limiter thereby prevents the rotary unit from rotatingthe inner shell relative to the outer shell in a manner that would causethe upstream blood pressure to exceed the maximum threshold, or thedownstream blood pressure to fall below the minimum threshold. Withoutthe rotary unit, torque cable 148 can also be manually rotated to obtaindesired upstream and downstream blood pressures. An audible alarm may beincorporated into the pressure limiter to sound when blood pressuresexceeds the thresholds. The pressure limiter may further comprise aninterlocking device. The interlocking device, in operative associationwith upstream and downstream tubes 152 and 154, can lock inner shell 136with respect to outer shell 118 as blood pressures approach the setthresholds. It should be noted that although the rotary unit, pressuremonitor, and pressure limiter are shown as separate units, they may beincorporated into an integral unit.

[0056] Referring to FIGS. 4A and 4B, the expanded constrictor comprisesouter conical shell 118 having base 120 and apex 122, and inner conicalshell 136 having base 138 and apex 140. The constrictor is preferablycomposed of a biocompatible material coated with heparin to preventblood clotting. The conical shape of the expanded constrictor minimizesturbulence caused by placement of the occluder in the vessel. The outerand inner shells include 2, 3, 4, 5, 6, or any other number of ports 128and 144, respectively, in communication with the conical interior topermit blood flow through the occluder. The inner shell can be rotatedrelative to the outer shell, so that ports 144 communicate with ports128. Apices 122 and 140 of the respective outer and inner shells furthercomprise collar 126 and 142. The collars may include engaging threads,so that collar 142 can be inserted and secured into collar 126, andbonded to a distal end of the torque cable, such that the inner shell iscoupled to and rotates with the torque cable. A rotary unit, preferablyincluding a stepper motor (not shown), may be mechanically coupled to aproximal end of the torque cable to provide precise rotational positionof the inner shell relative to the outer shell, thereby providingvariable flow through the occluder.

[0057] Instead of having the circular ports in the inner and outershells as depicted in FIGS. 4A and 4B, the constrictor may include 2, 3,4, 5, 6, or any other number of ports having other suitable geometricshapes. FIG. 5 depicts constrictor 104 having a plurality of portsconstructed as elongate rectangular slots 175.

[0058]FIG. 6 depicts another embodiment of the constrictor, whichcomprises beveled lip 140 having distal end 142 and proximal end 141.The proximal end is affixed to base 120 of the outer conical shell. Theproximal end has a larger diameter than the distal end and is everted toprevent the constrictor from being displaced in the direction of bloodflow, thereby securing the constrictor in the vessel.

[0059] Still another embodiment of the occluder may includes 1, 2, 3, 4,5, or any other number of graduated inflatable rings. In FIG. 7, ring151 is affixed to the base of the conical shell. Ring 153, having thesmallest inflated diameter, is attached to ring 152, which is thenattached to ring 151, having the largest inflatable diameter. The fullyinflated rings will have a thickness of approximately 2 to 3millimeters. Similar to the beveled lip of FIG. 8, the rings prevent theouter conical shell from being displaced in the direction of blood flow,thereby securing the constrictor in the vessel.

[0060] The flow rate of blood through the constrictor can be easilycontrolled by rotating inner conical shell 136 (shown with dotted lines)relative to outer conical shell 118 as depicted in FIGS. 8, 9, and 10.In FIG. 8, the inner shell is rotated so that ports 144 and 128 arecompletely misaligned, thereby achieving no flow through the ports andcomplete vascular occlusion distally. As the inner shell is rotatedclockwise relative to the second shell in FIG. 9, ports 144 on the innershell become partially aligned with ports 128 on the outer shell,thereby achieving partial flow through the ports and partial vascularocclusion. In FIG. 10, with continuing clockwise rotation of the innershell, ports 144 become completely aligned with ports 128, therebyachieving maximum flow through the ports. To provide a broader and morepredictable range of blood flow through the conduit, the ports of theinner and outer shells are preferably of equal size and number such thatthey may align with each other.

[0061]FIG. 11 depicts another embodiment of the occlusion device forpartial occlusion of blood flow in a vessel. Device 200 compriseselongate catheter 202, distally mounted expandable constrictor 204 withmaximum periphery 210, opening 224, and variable flow mechanism 208operatively associated with the constrictor. The catheter includesadapter 203 at its proximal end. Preferably, the device includesmanometer 212 and pressure limiter 214, and pressure monitor 240. Thepressure monitor records and displays blood pressure data received fromthe manometer. Longitudinal positioning unit 208, receiving signals frompressure limiter 214, and controls variable flow mechanism 208 toprovide variable blood flow through the constrictor.

[0062] Referring to FIG. 12, catheter 202 includes lumen 216.Constrictor 204 comprises hollow conical shell 218 having base 220 andapex 222. The inner circumference of the base forms opening 224, whichprovides a distal inlet for blood flow through the constrictor. Theinner circumference of apex 222 forms collar 228 with proximal opening226, which provide an outlet for blood flow through the constrictor. Theconical interior, disposed within shell 218, communicates with opening224 distally and opening 226 proximally. When the base of theconstrictor is positioned upstream in a vessel, blood flows into opening224, through the conical interior, and exits downstream through opening226. The catheter is bonded to collar 228 about a portion of its innercircumference. The constrictor is expanded by operation of ring 230, abeveled lip, or a series of graduated toroidal balloons as describedabove. The constrictor is collapsed and may be delivered to a vessellocation by using a guide sheath.

[0063] The manometer comprises upstream pressure tube 236 and downstreampressure tube 238, which are disposed in lumen 216 of the catheter andconnected proximally to a pressure monitor. The upstream pressure tubeextends distal from the constrictor or may be bonded to the innersurface of the conical shell, thereby providing upstream blood pressuremeasurement. The downstream pressure tube extends through an orifice inthe catheter proximal to the constrictor, thereby providing downstreamblood pressure measurement.

[0064] The variable flow mechanism comprises a plurality of flaps 230pivotally affixed to base 220. The flaps are preferably made of aresilient material, such as Nitinol, to resist movement caused by bloodflow through the conduit. A plurality of pull wires 232, disposedthrough lumen 216, are distally connected to flaps 230, such thatapplying a tensile force to the wires pivotally displaces flaps 230 fromtheir preformed position. Three of the flaps (shown in dotted lines) aredisplaced inward. Releasing the wires allows the resilient flaps torelax and return to their preformed position. The pull wires are coupledproximally to the longitudinal positioning unit, which provides precisedisplacement of the flaps relative to opening 224. Alternatively, wires232 can be manually tensed to operate the flaps. The pressure limiterreceives pressure measurements from the pressure monitor and transmitssignals to the longitudinal positioning unit to prevent the upstream anddownstream blood pressures from exceeding the set thresholds.

[0065]FIGS. 13A, 13B, 13C, and 13D depict frontal views of theconstrictor having flaps in various positions for controlling bloodflow. In FIG. 13A, preformed flaps 230 extend radially inward toward thelongitudinal axis of the catheter, as in the absence of a displacingforce, i.e., an external force other than that created by blood flow.When the constrictor is positioned in the descending aorta, for example,the size of opening 224 and blood flow through the opening is minimized,thereby providing maximal aortic occlusion. In the presence of adisplacing force, such as pulling the wires to displace flaps 230 fromtheir preformed position as depicted in FIG. 13B, the size of aperture224 and blood flow through the conduit increases, thereby providingpartial aortic occlusion.

[0066] Alternatively, preformed flaps 230 extend parallel to thelongitudinal axis of opening 224 in the absence of a displacing force asdepicted in FIG. 13C. The size of opening 224 and blood flow through theconduit are maximized, thereby providing minimal blood flow occlusion.In the presence of a displacing force, flaps 230 are pivotally displacedfrom their preformed position as depicted in FIG. 13D. The size ofopening 224 and blood flow through the opening are minimized, therebyproviding maximal blood flow occlusion. Thus, by pivotally displacingflaps 230 relative to opening 224, the size of the opening and flow ratethrough the constrictor is controlled to provide variable vesselocclusion.

[0067] The constrictor shown in FIG. 12 can be alternatively mounted oncatheter 202, such that base 220 is proximal to apex 222 as shown inFIG. 14A. In this embodiment, flaps 230 are formed on open apex 222.When constrictor 204 is inserted downstream in the aorta, for example,pressure tube 238 extends distally from opening 226 to providedownstream blood pressure measurements, whereas pressure tube 236extends proximally through an orifice in the catheter to provideupstream blood pressure measurements.

[0068] In FIG. 15, another embodiment of the device comprises catheter302, a distally mounted occluder 304 with maximum periphery 310, bloodpassage 306 disposed within the constrictor, and variable flow mechanism308 in operative association with the blood conduit. Inflation device334 communicates with the constrictor, and inflation device 338communicates with the variable flow mechanism. The device preferablyincludes proximal adapter 303, manometer 312, and pressure limiter 314.Pressure monitor 312 records and displays blood pressure data from themanometer. The pressure limiter is connected to the pressure monitor andto an interlocking valve on inflation device 338, such that the bloodpressure upstream and downstream the constrictor can be controlled toprevent from exceeding set thresholds.

[0069] Referring to FIG. 16, constrictor 304 is mounted to a distal endof catheter 302 having lumen 316. The constrictor comprises a sleeve orcylindrical balloon 318 having outer wall 320 and inner wall 322, whichenclose chamber 323. The cylindrical balloon has first end 324 withopening 328 and second end 326 with opening 330. Catheter 302 is bondedto inner wall 322 of the cylindrical balloon. Inflation tube 332, housedwithin lumen 316 of the catheter, communicates distally with thecylindrical balloon and proximally with a syringe or other inflationdevice. The cylindrical balloon can be expanded or collapsed byinjecting or removing air, saline, or other medium. Occlusion isprovided by toroidal balloon 334 disposed about the outer or innersurface of sleeve 318 and communicating with inflation tube 336 and asyringe. The inflation device may include an interlocking valve toprevent unintended deflation.

[0070] Lumen 306 communicates with opening 328 distally and opening 328proximally. When deployed in a vessel, blood flows through lumen 306 andexits downstream opening 330. The constrictor may further include ananchoring structure, shown in FIG. 16 as rings 333, which are disposedabout outer wall 320 of the cylindrical sleeve and define maximumperiphery 310 of the occluder.

[0071] Manometer 312 comprises upstream pressure tube 340 and downstreampressure tube 342, which are operatively connected proximally to apressure monitor. Pressure tube 340 is bonded to the lumen of thecylindrical balloon and extends distal to provide upstream bloodpressure measurements, while tube 342 emerges from the catheter proximalthe occluder to provide downstream blood pressure measurements.

[0072] In FIG. 17, fluid is injected to expand balloon 334, therebyconstricting sleeve 318. As a result, blood flow is constricted. In FIG.18, balloon deflation allows sleeve 318 to revert back to its pre-shapedgeometry, increasing blood flow therethrough. Thus, balloon 334 can beinflated and deflated to vary the cross-sectional diameter of lumen 306to vary flow rate.

[0073] The occlusion devices described herein can be employed with avariety of therapeutic catheters to treat vascular abnormalities. Forexample, as depicted in FIG. 19, suction/atherectomy catheter 402 can beinserted through lumen 306, such that the suction/atherectomy catheteris independently movable relative to occlusive device 300. Catheter 402includes elongate tube 404 and distally located aspiration port 406,cutting device 408, and balloon 410 for removing thromboembolic materialin a vessel.

[0074] In FIG. 20, infusion catheter 502 and EPS catheter 504 areinserted through opening 206 of occlusion device 200, such that catheter502 and 504 are independently movable relative to occlusion device 200.The infusion catheter, which includes elongate tube 506, distallylocated perfusion port 508, and expandable balloon 510, can be used toremove thromboembolic material in a vessel. EPS catheter 504, whichincludes elongate tube 512 and distally located ablation device 514, maybe used to map out or ablate an extra conduction pathway in themyocardial tissue, e.g., in patients suffering fromWolff-Parkinson-White syndrome. The occlusion device, capable ofaugmenting cerebral perfusion, is therefore useful not only infacilitating definitive treatment but also in cerebral ischemiaprevention during EPS and other cardiac interventions or cardiacsurgery, such as coronary catheterization, where sudden fall in cerebralblood flow may occur due to arrhythmia, myocardial infarction, orcongestive heart failure.

[0075] Referring to FIG. 21A, occlusion device 100 described above canbe used to partially occlude blood flow in aorta 10 of a patientsuffering from global cerebral ischemia due to, e.g., septic shock,congestive heart failure, or cardiac arrest. Constrictor 104 can beintroduced in its collapsed geometry through an incision on a peripheralartery, such as the femoral, subclavian, axillary, or radial artery,into the patient's aorta. A guide wire may first be introduced over aneedle, and the collapsed constrictor is then passed over the guide wireand the needle to position distal to the takeoff of left subclavianartery 20 in the descending aorta. The constrictor is expanded, suchthat maximum periphery 110 of the occluder, formed by expandable ring130, sealingly contacts the inner aortic wall. The position andorientation of the collapsed or expanded device can be checked by TEE,TTE, aortic arch cutaneous ultrasound in the emergency room, or IVUS andangiography in the angiogram suite.

[0076] The expanded constrictor is maintained during systole, duringdiastole, or during systole and diastole, during which blood distal tothe brachiocephalic artery is forced to pass through opening 106,thereby providing a continuous partial occlusion of aortic blood flow.Alternatively, partial occlusion of aortic blood flow can beintermittent. As a result, blood flow to the descending aorta ispartially diverted to brachiocephalic artery 16, left subclavian artery20, and left carotid artery 18, thereby augmenting blood flow to thecerebral vasculature. In treating global ischemia, such as in shock,cerebral perfusion is increased by increasing blood flow through bothcarotid and vertebral arteries. Additionally, blood flow to the aorta ispartially diverted to the coronary arteries by using the occlusiondevice, thereby augmenting flow to the coronary arteries. Using thepartial occlusion methods during systemic circulatory failure may,therefore, improve cardiac performance and organ perfusion. Byselectively increasing cerebral and coronary blood flow in this manner,the dosage of commonly used systemic vasoconstrictors, such as dopamineand norepinephrine, may be reduced or eliminated.

[0077] Alternatively, the device of FIG. 14, much like the device usedto extinguish the flame of a candle, can be introduced through anincision on left subclavian artery 36 as depicted in FIG. 21B.Constrictor 204 is inserted in aorta 22 distal to the takeoff of theleft subclavian artery to provide partial, variable, and/or continuousaortic occlusion and is advanced antegrade into the descending aorta.This device is particularly useful in situations where peripheralincision can not be made on the femoral arteries due toarteriosclerosis, thrombosis, aneurysm, or stenosis.

[0078] The devices and methods described in FIGS. 21A and 21B are usefulin treating stroke patients within few minutes of stroke symptom, andthe treatment can be continued up to 96 hours or more. For example, intreating focal ischemia due to a thromboembolic occlusion in the rightinternal carotid artery the constrictor may be position distal to thetakeoff of the left subclavian. As a result, blood flow is diverted tobrachiocephalic artery 16 and left CCA to augment both ipsilateral andcontralateral collateral circulation by reversing direction of flowacross the Circle of Willis, i.e., increasing flow in the right externalcarotid artery and left common carotid artery. The collateral cerebralcirculation is further described in details in co-pending U.S.application Ser. No. [Lyon & Lyon Docket No. 239/096], incorporatedherein by reference.

[0079] In treating focal ischemia due to a thromboembolic occlusion inthe left internal carotid artery, for example, the constrictor can bepositioned proximal to the takeoff of left carotid artery 18 and distalto the takeoff of brachiocephalic artery 16 as shown in FIG. 22.Contralateral collateral enhancement is provided by increasing flowthrough the brachiocephalic artery, thereby reversing blood flow in theright posterior communicating artery, right PCA, left posteriorcommunicating artery 68 and anterior communicating artery, resulting inincreased perfusion to the ischemic area distal to the occlusion andminimizing neurological deficits. Alternatively, the constrictor may bepositioned distal to the takeoff of the left subclavian artery toprovide both ipsilateral and contralateral collateral augmentation.Ipsilateral circulation is enhanced by increasing flow through the leftexternal carotid artery and reversing flow along the left ophthalmicartery, both of which contribute to increased flow in the left ICAdistal to the occlusion.

[0080] As a result of partially occluding aortic blood flow, bloodpressure distal to the aortic occlusion may decrease, and this mayresult in a reduction in renal output. Blood pressure proximal theaortic occlusion will increase and may result in excessive rostralhypertension. The blood pressures, measured by the manometer, aremonitored continuously, and based on this information the occlusion isadjusted to avoid peripheral organ damage. After resolution of thecerebral ischemia, the constrictor is collapsed and removed, therebyremoving the aortic occlusion and restoring normal blood flow in theaorta.

[0081] In FIG. 23, constrictor 304 is inserted in aorta 10 and can beused to remove thromboembolic material 72 from left common carotidartery 18, while augmenting and maintaining cerebral perfusion distal tothe occluding lesion. The occluder may be introduced through a guidesheath until it is positioned distal to left subclavian artery 20. Inemergency situations, the constrictor can be inserted through a femoralincision in the emergency room, and atherectomy/suction catheter 402 canbe inserted through the constrictor under angioscopic vision in theangiogram suite after the patient is stabilized hemodynamically. Theatherectomy/suction catheter, which includes expandable balloon 410,distal aspiration port 406, and atherectomy device 408, is introducedthrough opening 306 until its distal end is positioned in left commoncarotid artery 18 proximal to the thromboembolic occlusion.

[0082] Constrictor 304 is then expanded to partially occlude aorticblood flow, thereby increasing perfusion to the ischemic region distalto the occluding lesion by enhancing ipsilateral collateral flow throughleft external carotid artery 46 and left vertebral artery 34 andcontralateral collateral flow to right carotid artery 24 and rightvertebral artery 28. The variable flow mechanism of constrictor 304 canbe adjusted to control blood flow to the cerebral vasculature and theblood pressure. Balloon 410 of catheter 402 is expanded in the leftcommon carotid artery, thereby creating a closed chamber betweenconstrictor 410 and the thromboembolic occlusion. Suction can be appliedto aspiration port 406 to create a negative pressure in the closedchamber, thereby increasing the pressure differential across thethromboembolic occlusion, which may dislodge the occluding lesion ontothe aspiration port and remove the occluding lesion. Thromboembolicmaterial 72 may be further removed by atherectomy device 408. Themethods herein can also be used to remove thromboembolic occlusion inthe vertebral artery. The occlusion device 304, therefore, not onlyaugments cerebral perfusion in patients suffering from focal stroke orglobal ischemia, but also maintains cerebral perfusion while waiting forinvasive or noninvasive intervention. The devices and methods of usingatherectomy/suction catheter 102 are further described in copending U.S.application Ser. No. [Lyon & Lyon Docket No. 239/096], incorporatedherein by reference.

[0083] During abdominal aortic aneurysm (AAA) surgery, lumbar or spinalarteries, which provide blood supply to the spinal cord, are oftendissected away from the diseased abdominal aorta, resulting in reductionof blood flow to the spinal cord. The devices herein disclosed may beused to condition the spinal cord prior to AAA repair, thereby reducingthe damage resulting from spinal ischemia during surgery. In FIG. 24,constrictor 104 is inserted in aorta 10 and expanded preferably distalto left subclavian artery 20 and proximal to lumbar arteries 38. As aresult, blood flow to the lumbar or spinal arteries is reduced. Whenthis device is used in patients anticipating a major thoracoabdominalsurgery, such as AAA repair, approximately 24 hours prior to surgery,blood flow to the lumbar arteries can be intentionally reduced to inducemild spinal ischemia, thereby conditioning the spinal cord to produceneuroprotective agents which may protect the spinal cord from moresignificant ischemic insult during surgery.

[0084] In hypertension, end organ damage often results, e.g., cardiac,renal, and cerebral ischemia and infarction. The devices and methodsherein may be employed in hypertension to protect the kidneys fromischemic insult. In FIG. 25, constrictors 104, which can be introducedthrough a femoral artery, are inserted in right renal artery 80 and leftrenal artery 82. The constrictors are expanded to partially occludeblood flow from descending aorta 10 to the renal arteries, therebyreducing blood pressure distal to the occlusion. The constrictors can bedeployed for the duration of any systemic hypertensive condition,thereby protecting the kidneys from damage that might otherwise becaused by the hypertension.

[0085] The length of the catheter will generally be between 20 to 150centimeters, preferably approximately between 30 and 100 centimeters.The inner diameter of the catheter will generally be between 0.2 and 0.6centimeters, preferably approximately 0.4 centimeters. The diameter ofthe base of the outer conical shell will generally be between 0.3 and3.0 centimeters, preferably approximately 0.5 and 2.0 centimeters. Thediameter of the inflated balloon occluder will generally be between 0.3and 3.0 centimeters, preferably approximately 0.5 and 2.0 centimeters.The ports of the inner and outer conical shells will generally have adiameter of between 1 to 6 millimeters, preferably approximately 3 to 4millimeters. The foregoing ranges are set forth solely for the purposeof illustrating typical device dimensions. The actual dimensions of adevice constructed according to the principles of the present inventionmay obviously vary outside of the listed ranges without departing fromthose basic principles.

[0086] Although the foregoing invention has, for the purposes of clarityand understanding, been described in some detail by way of illustrationand example, it will be obvious that certain changes and modificationsmay be practiced which will still fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for increasing cerebral blood flow,comprising the steps of: advancing a catheter into the descending aorta,the catheter having a proximal region, a distal region, and anexpandable member mounted on the distal region; locating the expandablemember downstream from the takeoff of a carotid artery; expanding theexpandable member to at least partially obstruct blood flow in the aortaduring systole and diastole; measuring a physiologic parameter thatindicates adequacy of cerebral perfusion; and adjusting the expansion ofthe expandable member based on the measured physiologic parameter. 2.The method of claim 1, wherein the physiologic parameter is bloodpressure.
 3. The method of claim 1, wherein the physiologic parameter iscerebral blood flow.
 4. The method of claim 1, wherein the expandablemember is a balloon.
 5. The method of claim 1, wherein the step ofexpanding the expandable member includes maintaining the expandablemember in an expanded condition during systole and diastole.
 6. Themethod of claim 1, wherein blood flow to the cerebral vasculatureincreases by at least 20%.
 7. The method of claim 1, wherein thecatheter is first inserted into a peripheral artery, and then advancedinto the descending aorta.
 8. A method for increasing cerebral bloodflow, comprising the steps of: advancing a catheter into the descendingaorta, the catheter having a proximal region, a distal region, and anexpandable member mounted on the distal region; locating the expandablemember downstream from the takeoff of a carotid artery; expanding theexpandable member to at least partially obstruct blood flow in the aortaduring systole and diastole; measuring a physiologic parameter; andadjusting the expansion of the expandable member if the measuredphysiologic parameter falls outside of a predetermined range.
 9. Themethod of claim 8, wherein the physiologic parameter is blood pressure.10. The method of claim 8, wherein the physiologic parameter is cerebralblood flow.
 11. The method of claim 8, wherein the expandable member isa balloon.
 12. The method of claim 8, wherein the step of expanding theexpandable member includes maintaining the expandable member in anexpanded condition during systole and diastole.
 13. The method of claim8, wherein blood flow to the cerebral vasculature increases by at least20%.
 14. The method of claim 8, wherein the catheter is first insertedinto a peripheral artery, and then advanced into the descending aorta.15. A method for increasing cerebral blood flow, comprising the stepsof: advancing a catheter into the descending aorta, the catheter havinga proximal region, a distal region, and an expandable member mounted onthe distal region; locating the expandable member downstream from thetakeoff of a carotid artery; expanding the expandable member to at leastpartially obstruct blood flow in the aorta; measuring a physiologicparameter that indicates adequacy of cerebral perfusion; and adjustingthe expansion of the expandable member based on the measured physiologicparameter.
 16. The method of claim 15, wherein the physiologic parameteris blood pressure.
 17. The method of claim 15, wherein the physiologicparameter is cerebral blood flow.
 18. The method of claim 15, whereinthe expandable member is a balloon.
 19. The method of claim 15, whereinthe step of expanding the expandable member includes maintaining theexpandable member in an expanded condition during systole and diastole.20. The method of claim 15, wherein blood flow to the cerebralvasculature increases by at least 20%.
 21. The method of claim 15,wherein the catheter is first inserted into a peripheral artery, andthen advanced into the descending aorta.
 22. A method for increasingcerebral blood flow, comprising the steps of: advancing a catheter intothe descending aorta, the catheter having a proximal region, a distalregion, and a balloon mounted on the distal region; locating the balloondownstream from the takeoff of a carotid artery; expanding the balloonby inflating with liquid to at least partially obstruct blood flow inthe aorta; measuring a physiologic parameter; and adjusting theexpansion of the expandable member based on the measured physiologicparameter.
 23. The method of claim 22, wherein the physiologic parameteris blood pressure.
 24. The method of claim 22, wherein the physiologicparameter is cerebral blood flow.
 25. The method of claim 22, whereinthe step of expanding the balloon includes maintaining the balloon in anexpanded condition during systole and diastole.
 26. The method of claim22, wherein blood flow to the cerebral vasculature increases by at least20%.
 27. The method of claim 22, wherein the catheter is first insertedinto a peripheral artery, and then advanced into the descending aorta.28. A method for increasing cerebral blood flow, comprising the stepsof: providing a catheter having a proximal end, a distal end, and anexpandable member mounted on the distal end, and a lumen extending fromthe proximal end and communicating with a port distal the expandablemember; advancing the distal end of the catheter into the descendingaorta; locating the expandable member downstream from the takeoff of acarotid artery; and expanding the expandable member to at leastpartially obstruct blood flow in the aorta during systole and diastole,wherein blood pressure or wave form in the proximal aorta is altered.29. The method of claim 28, wherein blood pressure in the proximal aortaincreases and blood pressure in the distal aorta decreases.
 30. Themethod of claim 28, wherein the step of expanding the expandable memberincludes maintaining the expanded expandable member during systole. 31.The method of claim 28, further comprising the step of advancing amedical instrument through the lumen, beyond the distal port, and intoan artery that branches from the aorta, wherein the medical instrumentis selected from the group consisting of a guiding catheter, an infusioncatheter, an angioplasty catheter, a laser catheter, an angiographycatheter, a therapeutic ultrasound catheter, a hypothermia catheter, astent catheter, an imaging catheter, a perfusion catheter, anatherectomy catheter, an occlusion catheter, an EP catheter, and anaspiration catheter.
 32. The method of claim 31, wherein the medicalinstrument is an interventional instrument.
 33. The method of claim 32,wherein the interventional instrument is selected from the groupconsisting of an infusion catheter, an angioplasty catheter, a lasercatheter, an angiography catheter, a therapeutic ultrasound catheter, ahypothermia catheter, a stent catheter, an imaging catheter, a perfusioncatheter, an atherectomy catheter, an occlusion catheter, an EPcatheter, and an aspiration catheter.
 34. A method for increasingcerebral blood flow, comprising the steps of: providing a catheterhaving a proximal end, a distal end, and an expandable member mounted onthe distal end, and a lumen extending from the proximal end andcommunicating with a port distal the expandable member; advancing thedistal end of the catheter into the descending aorta; locating theexpandable member downstream from the takeoff of a carotid artery; andexpanding the expandable member to at least partially obstruct bloodflow in the aorta during systole and diastole, wherein blood pressure inthe proximal aorta is altered.
 35. The method of claim 34, wherein bloodpressure in the proximal aorta increases and blood pressure in thedistal aorta decreases.
 36. The method of claim 34, wherein the step ofexpanding the expandable member includes maintaining the expandedexpandable member during systole.
 37. The method of claim 34, furthercomprising the step of advancing a medical instrument through the lumen,beyond the distal port, and into an artery that branches from the aorta,wherein the medical instrument is selected from the group consisting ofa guiding catheter, an infusion catheter, an angioplasty catheter, alaser catheter, an angiography catheter, a therapeutic ultrasoundcatheter, a hypothermia catheter, a stent catheter, an imaging catheter,a perfusion catheter, an atherectomy catheter, an occlusion catheter, anEP catheter, and an aspiration catheter.
 38. The method of claim 37,wherein the medical instrument is an interventional instrument.
 39. Themethod of claim 38, wherein the interventional instrument is selectedfrom the group consisting of an infusion catheter, an angioplastycatheter, a laser catheter, an angiography catheter, a therapeuticultrasound catheter, a hypothermia catheter, a stent catheter, animaging catheter, a perfusion catheter, an atherectomy catheter, anocclusion catheter, an EP catheter, and an aspiration catheter.
 40. Amethod for increasing cerebral blood flow, comprising the steps of:providing a catheter having a proximal end, a distal end, and anexpandable member mounted on the distal end; inserting the distal end ofthe catheter into the descending aorta; locating the expandable memberdownstream from the takeoff of a carotid artery; and expanding theexpandable member to at least partially obstruct blood flow in the aortaand maintaining the expanded expandable member during systole, andwherein blood flow to the cerebral vasculature increases and alters thepulse wave.
 41. The method of claim 40, wherein blood flow to thecerebral vasculature increases and exaggerates the pulse wave to enhancethe pulsatile wave form.
 42. The method of claim 40, wherein bloodpressure in the proximal aorta increases and blood pressure in thedistal aorta decreases.
 43. The method of claim 40, further comprisingthe steps of: measuring a first blood pressure at a location distal theexpandable member; and adjusting the expandable member based on thefirst measured blood pressure.
 44. The method of claim 43, furthercomprising the step of measuring a second blood pressure at a locationproximal the expandable member, and wherein the expandable member isadjusted based on a comparison of the first and second measured bloodpressures.
 45. The method of claim 40, wherein the expandable membercomprises a balloon having proximal and distal ends separated by alength of no more than 20 cm.
 46. A method for increasing cerebral bloodflow, comprising the steps of: providing a catheter having a proximalend, a distal end, and an expandable member mounted on the distal end;advancing the distal end of the catheter into the descending aorta;locating the expandable member downstream from the takeoff of a carotidartery; expanding the expandable member to at least partially obstructblood flow in the aorta during systole and diastole; measuring a firstblood pressure at a location proximal the expandable member andmeasuring a second blood pressure at a location distal the expandablemember; and adjusting the expandable member based on a comparison of thefirst and second measured blood pressures.
 47. The method of claim 46,wherein blood pressure in the proximal aorta increases and bloodpressure in the distal aorta decreases.
 48. The method of claim 46,wherein the step of expanding the expandable member includes maintainingthe expanded expandable member during systole.
 49. A method forincreasing cerebral blood flow, comprising the steps of: providing acatheter having a proximal end, a distal end, and an expandable membermounted on the distal end; advancing the distal end of the catheter intothe descending aorta; locating the expandable member downstream from thetakeoff of a carotid artery; expanding the expandable member to at leastpartially obstruct blood flow in the aorta during systole and diastole;measuring a first blood pressure at one of a location proximal or distalthe expandable member; and adjusting the expandable member based on acomparison of the first and second measured blood pressures.
 50. Themethod of claim 49, further comprising the step of measuring a secondblood pressure at the other of a location proximal or distal theexpandable member.
 51. The method of claim 49, wherein blood pressure inthe proximal aorta increases and blood pressure in the distal aortadecreases.
 52. The method of claim 49, wherein the step of expanding theexpandable member includes maintaining the expanded expandable memberduring systole.
 53. A method for increasing cerebral blood flow,comprising the steps of: providing a catheter having a proximal end, adistal end, and an expandable member mounted on the distal end;advancing the distal end of the catheter into the descending aorta;locating the expandable member downstream from the takeoff of a carotidartery; expanding the expandable member to at least partially obstructblood flow in the aorta during systole and diastole; measuring aphysiologic parameter; and adjusting the expansion of the expandablemember if the measured physiologic parameter falls outside of apredetermined range.
 54. The method of claim 53, wherein blood pressurein the proximal aorta increases and blood pressure in the distal aortadecreases.
 55. The method of claim 53, wherein the step of expanding theexpandable member includes maintaining the expanded expandable memberduring systole.